HMDs are used to present virtual scenery to a user, or to augment real scenery with virtual information or virtual objects. An HMD typically includes a pixelated electronic display, which displays images by selectively exciting display pixels and/or color sub-pixels to a various degree of luminance. The number of display pixels per unit area, or pixel density, defines a native resolution of the display. Imaging optics may be present that presents the displayed images to the user with magnification, thereby magnifying the display pixels for the user.
Humans with normal visual acuity, typically identified as 20/20 vision, can distinguish two points separated by an angle of one minute of arc (1′), which is the sharpest eyesight observed in the foveola. Within about +/−10° of the foveola, the visual acuity drops to 20/100, which correspond to a resolution angle of 5′. Thus, a typical human eye with the 20/20 sight can resolve two pixels in an image if the light rays they emit enter the eye at an angle to each other as small as 1′. However, the pixel density of an electronic display may be insufficient to directly support the ultimate resolution of a human eye; for example, rays emitted by neighboring pixels of an electronic display used in a typical HDM may enter the eye at an angle greater than 1′, and the user perception of the displayed image may suffer because of that. In addition, some displays have relatively small light emitting areas that are surrounded by interstitial areas from which no light emanates. These interstitial areas are typically dark and may lead to a visual artifact known as screen door when the viewer is able to visually resolve the dark and active areas of the pixels.